During orthodontic treatment, it is often desirable, and in some cases necessary, to create molds or other impressions of an orthodontic patient's teeth. When conventional orthodontic brackets are not mounted on the patient's teeth, a variety of suitable molding compounds and impression methods may be used. However, when conventional orthodontic brackets are installed on the patient's teeth, the range of suitable molding compounds and impression methods is much more limited, especially when it is desirable or necessary to accurately reproduce the position of the archwire-receiving slot, which is defined by the orthodontic brackets, relative to the patent's teeth.
Many conventional molding compounds, or materials, that are suitable for creating molds or impressions of a patient's teeth prior to the installation of orthodontic brackets are unsuitable for creating impressions of the patient's teeth while the brackets are installed. While these compounds, an example of which is polyvinylsiloxane, are suitable for creating very accurate molds of the patient's teeth, including impressions that are suitable for destructive scanning, or imaging, processes, the molding compounds set, or cure, so solidly that they are likely to debond (detach or otherwise remove) orthodontic brackets from the patient's teeth, damage the orthodontic brackets, and/or deform or otherwise damage or distort the mold during the removal process from the patient's teeth (and installed orthodontic brackets). Specifically, the bracket is typically connected to a patient's tooth with an adhesive that is not strong enough to withstand the imparted forces as the set molding material, or mold, which also extends around the brackets, is drawn away from the patient's teeth. As a result, this removal of the mold may debond the bracket from the tooth as the mold is removed from the patient's teeth. Such a rigid impression material is also prone to solidifying around the undercuts, wings, or other projecting portions of an orthodontic bracket and thereby prevent nondeformable removal of the mold without damaging the bracket or the mold.
Other molding compounds are suitable for making impressions of the patient's teeth even after the installation of orthodontic brackets, but these molding compounds are formed from materials that are sufficiently flexible, soft, and/or deformable that they are not suitable to create molds for use in some orthodontic applications, such as applications where very accurate, or detailed, representations of the patient's teeth and attached brackets are needed. One example of such a compound is alginate, a natural polymer. Such materials, once set, are likely to tear, deform, or otherwise distort during removal of the set molding compound, thereby rendering the resulting mold unable to accurately reproduce the position of the brackets and/or archwires relative to the patient's teeth.
A further method of creating very accurate representations of a patient's teeth after orthodontic brackets are installed involves the use of CT scanners or other intra-oral scanners that create images of the patient's teeth, including any attached orthodontic brackets. These images may be used to make electronic or other models or representations of the patient's teeth and the attached orthodontic brackets. However, this scanning process requires expensive scanning equipment and takes considerable time and practitioner attention (especially when compared to using molding compounds).